DMRS for 5G things communication system

ABSTRACT

Systems and methods of providing DMRS for a UE are generally described. The DMRS locations in a resource unit of a Physical Resource Allocation of a shared channel are randomly determined, and the DMRS sequences randomly generated before transmission from a master UE to a wearable UE. The DMRS locations are disposed on different subcarriers and symbols in the resource unit and are repeated every k subframes or m resource units within the same subframe. In situations in which the collision/contention probability is relatively small, DMRS in control channels may be used rather than in the shared data channel.

PRIORITY CLAIM

This application is a U.S. National Stage Filing under 35 U.S.C. 371from International Application No. PCT/US2016/059300, filed Oct. 28,2016 and published in English as WO 2017/146779 on Aug. 31, 2017, whichclaims the benefit of priority to U.S. Provisional Patent ApplicationSer. No. 62/329,047 filed Apr. 28, 2016, entitled “SUBFRAME STRUCTUREFOR COMMUNICATION OF UNDERLAY INFRASTRUCTURE LESS NETWORKS,” U.S.Provisional Patent Application Ser. No. 62/375,232, filed Aug. 15, 2016,and U.S. Provisional Patent Application Ser. No. 62/300,332, filed Feb.26, 2016, each of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

Embodiments pertain to radio access networks. Some embodiments relate towearable devices in various cellular and wireless local area network(WLAN) networks, including Third Generation Partnership Project LongTerm Evolution (3GPP LTE) networks and LTE advanced (LTE-A) networks aswell as 4^(th) generation (4G) networks and 5^(th) generation (5G)networks. Some embodiments relate to 5G wearable devices and networkinteractions, in particular reference signal design.

BACKGROUND

The use of 3GPP LTE systems (including both LTE and LTE-A systems) hasincreased due to both an increase in the types of devices user equipment(UEs) using network resources as well as the amount of data andbandwidth being used by various applications, such as video streaming,operating on these UEs. For example, the growth of network use byInternet of Things (IoT) UEs, which include machine type communication(MTC) devices such as sensors and may use machine-to-machine (M2M)communications, has severely strained network resources. New 3GPPstandard releases related to the next generation network (5G) are takinginto account the massive influx of low-data, high-delay and low powertransmissions.

One type of user-based IoT devices developed recently whose popularityhas exploded is IoT wearable devices. Unlike many MTC IoT devices,wearable devices may have a mobility similar to that of cell phones anda greater, albeit still limited, functionality. Wireless systems,however, may have a number of issues adapting to the various IoTdevices. For example, existing wireless systems may be unable to handlethe simultaneous needs of multiple wearable devices, which may includeaccess to another device as well as communication using short/sparsedata transmissions even in the risk of collisions at the receiver.Consequently, the next generation (5G) network may be designed to reduceunnecessary power consumption and resource waste by channel selectionand estimation techniques using well designed reference signals toalleviate some of these issues.

BRIEF DESCRIPTION OF THE FIGURES

In the figures, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The figures illustrate generally, by way of example, but notby way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is a block diagram of a system architecture for supportingwearable devices in accordance with some embodiments.

FIG. 2 illustrates components of a communication device in accordancewith some embodiments.

FIG. 3 illustrates a block diagram of a communication device inaccordance with some embodiments.

FIG. 4 illustrates another block diagram of a communication device inaccordance with some embodiments.

FIG. 5 illustrates a frame structure in accordance with someembodiments.

FIGS. 6A-D illustrate Demodulation Reference Signal (DMRS) locations inaccordance with some embodiments.

FIG. 7 illustrates DMRS locations in a Resource Unit in accordance withsome embodiments.

FIG. 8 illustrates a flowchart of DMRS generation in accordance withsome embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims.

FIG. 1 is a block diagram of a system architecture 100 for supportingwearable devices. As shown, the system architecture 100 includes anetwork user equipment (nUE) 110, one or more things user equipment(tUEs) 120 a, 120 b, 120 c, an evolved universal terrestrial radioaccess network (EUTRAN) base station (BS, also referred to as an evolvedNodeB (eNB)) or 5G base station 130, and an evolved packet core (EPC) or5G core 140. The nUE 110 and the tUEs 120 together form a personal areanetwork (PAN) 150 or side link cell.

The nUE 110 may be any user equipment capable of communicating with thebase station 130 via an air interface. According to some examples, thenUE 110 may be a mobile phone, a tablet computer, a wearable device suchas a smart watch, etc. According to some examples, the nUE may be a tUEthat is capable of communicating with the base station 130 and hassufficient battery life (e.g., greater than 30%, 50%, 75%, 90% of themaximum amount of battery power etc.). The nUE 110 may have a fullinfrastructure network access protocol and full control and user plane(C/U-plane) functions. As shown, the nUE 110 may communicate with thebase station 130 via a Xu-d (direct) air interface.

Each tUE 120 may include a wireless interface (Xu-d or Xu-s) forcommunicating within the PAN 150. The tUE 120 may communicate with thenUE 110 or another tUE 120 through the Xu-s (sidelink) intra-PAN airinterface. The tUE 120 may include, for example, smart watches, smartglasses, smart headphones, fitness sensors, movement trackers, sleepsensors, etc. The tUE 120 may also communicate directly with the basestation 130 via a Xu-d air interface. The nUE 110 may act as a master UEin a sidelink cell formed by the nUE 110 and associated tUEs 120. ThetUE 120 may have a full sidelink protocol stack and may or may not havestandalone direct link protocol stack. The tUE 120 may act as a slave UEin the side link cell. The nUE 110 may communicate data of the tUE 120(either direct data or data of the tUE 120 modified by the nUE 110) tothe base station 130. The data may be wearable UE data, for example,health related data or limited communication data, such as text data.

The base station 130 may be a base station of a cellular network. Thebase station 130 is may be an eNB in a LTE cellular network or a 5GRadio Access Network (RAN) in a next generation (5G) network. In thelatter case, the 5G RAN may be a standalone base station or a boostercell anchored to an eNB. The base station 130 may communicate with acore network 140 (EPC for LTE or 5G core for 5G) using an S1 interface.Some aspects of the subject technology are directed to defining the airinterface between the base station and the PAN of the nUE 110 and thetUEs 120, while other aspects are directed to defining the intra-PAN airinterface for enabling low power operation with diverse traffic andapplication requirements.

Some aspects of the subject technology may be implemented in conjunctionwith a LTE network, and, in some cases, leverages device-to-device (D2D)and machine-type communications (MTC) technology. However, forconnectivity techniques, aspects of the subject technology addresshigh-density scenarios. For LTE-D2D, some aspects of the subjecttechnology enable PAN-specific identity, unicast in intra-PANcommunication, uplink and downlink features, and operation in unlicensedbands. For LTE-MTC, some aspects of the subject technology providesupport for diverse traffic, including high rate traffic and low latencytraffic.

The base station 130 may be a macro base station or a smaller basestation (micro, pico, nano) that may terminate the air interfaceprotocol. In some embodiments, the base station 130 may fulfill variouslogical functions for the RAN including, but not limited to, RNC (radionetwork controller functions) such as radio bearer management, uplinkand downlink dynamic radio resource management and data packetscheduling, and mobility management. In accordance with embodiments, UEs120 may be configured to communicate orthogonal frequency divisionmultiplexed (OFDM) communication signals with the base station 130 overa multicarrier communication channel in accordance with an OFDMAcommunication technique. The OFDM signals may comprise a plurality oforthogonal subcarriers. In other embodiments, such as those related to5G systems, non-OFDM signals may be used in addition or instead of OFDMsignals.

The S1 interface may be the interface that separates the RAN 130 and thecore network 140. The S1 interface may be split into two parts: theS1-U, which may carry traffic data between base stations of the RAN 130and other elements of the core network, such as a serving GW, and theS1-MME, which may be a signaling interface between the RAN 130 and anMME.

FIG. 2 illustrates components of a communication device in accordancewith some embodiments. The communication device 200 may be a UE, eNB orother network component as described herein. The communication device200 may be a stationary, non-mobile device or may be a mobile device. Insome embodiments, the UE 200 may include application circuitry 202,baseband circuitry 204, Radio Frequency (RF) circuitry 206, front-endmodule (FEM) circuitry 208 and one or more antennas 210, coupledtogether at least as shown. At least some of the baseband circuitry 204,RF circuitry 206, and FEM circuitry 208 may form a transceiver. In someembodiments, other network elements, such as the MME may contain some orall of the components shown in FIG. 2.

The application or processing circuitry 202 may include one or moreapplication processors. For example, the application circuitry 202 mayinclude circuitry such as, but not limited to, one or more single-coreor multi-core processors. The processor(s) may include any combinationof general-purpose processors and dedicated processors (e.g., graphicsprocessors, application processors, etc.). The processors may be coupledwith and/or may include memory/storage and may be configured to executeinstructions stored in the memory/storage to enable various applicationsand/or operating systems to run on the system.

The baseband circuitry 204 may include circuitry such as, but notlimited to, one or more single-core or multi-core processors. Thebaseband circuitry 204 may include one or more baseband processorsand/or control logic to process baseband signals received from a receivesignal path of the RF circuitry 206 and to generate baseband signals fora transmit signal path of the RF circuitry 206. Baseband processingcircuity 204 may interface with the application circuitry 202 forgeneration and processing of the baseband signals and for controllingoperations of the RF circuitry 206. For example, in some embodiments,the baseband circuitry 204 may include a second generation (2G) basebandprocessor 204 a, third generation (3G) baseband processor 204 b, fourthgeneration (4G) baseband processor 204 c, and/or other basebandprocessor(s) 204 d for other existing generations, generations indevelopment or to be developed in the future (e.g., fifth generation(5G), 5G, etc.). The baseband circuitry 204 (e.g., one or more ofbaseband processors 204 a-d) may handle various radio control functionsthat enable communication with one or more radio networks via the RFcircuitry 206. The radio control functions may include, but are notlimited to, signal modulation/demodulation, encoding/decoding, radiofrequency shifting, etc. In some embodiments, modulation/demodulationcircuitry of the baseband circuitry 204 may include FFT, precoding,and/or constellation mapping/demapping functionality. In someembodiments, encoding/decoding circuitry of the baseband circuitry 204may include convolutional, tail-biting convolutional, turbo, Viterbi,and/or Low Density Parity Check (LDPC) encoder/decoder functionality.Embodiments of modulation/demodulation and encoder/decoder functionalityare not limited to these examples and may include other suitablefunctionality in other embodiments.

In some embodiments, the baseband circuitry 204 may include elements ofa protocol stack such as, for example, elements of an Evolved UTRAN(EUTRAN) protocol including, for example, physical (PHY), media accesscontrol (MAC), radio link control (RLC), packet data convergenceprotocol (PDCP), radio resource control (RRC) elements, and/orNon-Access Stratum (NAS) elements. A central processing unit (CPU) 204 eof the baseband circuitry 204 may be configured to run elements of theprotocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRClayers, and/or NAS. In some embodiments, the baseband circuitry mayinclude one or more audio digital signal processor(s) (DSP) 204 f. Theaudio DSP(s) 204 f may be include elements for compression/decompressionand echo cancellation and may include other suitable processing elementsin other embodiments. Components of the baseband circuitry may besuitably combined in a single chip, a single chipset, or disposed on asame circuit board in some embodiments. In some embodiments, some or allof the constituent components of the baseband circuitry 204 and theapplication circuitry 202 may be implemented together such as, forexample, on a system on a chip (SOC).

In some embodiments, the baseband circuitry 204 may provide forcommunication compatible with one or more radio technologies. Forexample, in some embodiments, the baseband circuitry 204 may supportcommunication with an EUTRAN and/or other wireless metropolitan areanetworks (WMAN), a wireless local area network (WLAN), a wirelesspersonal area network (WPAN). Embodiments in which the basebandcircuitry 204 is configured to support radio communications of more thanone wireless protocol may be referred to as multi-mode basebandcircuitry. In some embodiments, the device can be configured to operatein accordance with communication standards or other protocols orstandards, including Institute of Electrical and Electronic Engineers(IEEE) 802.16 wireless technology (WiMax), IEEE 802.11 wirelesstechnology (WiFi) including IEEE 802.11 ad, which operates in the 60 GHzmillimeter wave spectrum, various other wireless technologies such asglobal system for mobile communications (GSM), enhanced data rates forGSM evolution (EDGE), GSM EDGE radio access network (GERAN), universalmobile telecommunications system (UMTS), UMTS terrestrial radio accessnetwork (UTRAN), or other 2G, 3G, 4G, 5G, etc. technologies eitheralready developed or to be developed.

RF circuitry 206 may enable communication with wireless networks usingmodulated electromagnetic radiation through a non-solid medium. Invarious embodiments, the RF circuitry 206 may include switches, filters,amplifiers, etc. to facilitate the communication with the wirelessnetwork. RF circuitry 206 may include a receive signal path which mayinclude circuitry to down-convert RF signals received from the FEMcircuitry 208 and provide baseband signals to the baseband circuitry204. RF circuitry 206 may also include a transmit signal path which mayinclude circuitry to up-convert baseband signals provided by thebaseband circuitry 204 and provide RF output signals to the FEMcircuitry 208 for transmission.

In some embodiments, the RF circuitry 206 may include a receive signalpath and a transmit signal path. The receive signal path of the RFcircuitry 206 may include mixer circuitry 206 a, amplifier circuitry 206b and filter circuitry 206 c. The transmit signal path of the RFcircuitry 206 may include filter circuitry 206 c and mixer circuitry 206a. RF circuitry 206 may also include synthesizer circuitry 206 d forsynthesizing a frequency for use by the mixer circuitry 206 a of thereceive signal path and the transmit signal path. In some embodiments,the mixer circuitry 206 a of the receive signal path may be configuredto down-convert RF signals received from the FEM circuitry 208 based onthe synthesized frequency provided by synthesizer circuitry 206 d. Theamplifier circuitry 206 b may be configured to amplify thedown-converted signals and the filter circuitry 206 c may be a low-passfilter (LPF) or band-pass filter (BPF) configured to remove unwantedsignals from the down-converted signals to generate output basebandsignals. Output baseband signals may be provided to the basebandcircuitry 204 for further processing. In some embodiments, the outputbaseband signals may be zero-frequency baseband signals, although thisis not a requirement. In some embodiments, mixer circuitry 206 a of thereceive signal path may comprise passive mixers, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 206 a of the transmit signalpath may be configured to up-convert input baseband signals based on thesynthesized frequency provided by the synthesizer circuitry 206 d togenerate RF output signals for the FEM circuitry 208. The basebandsignals may be provided by the baseband circuitry 204 and may befiltered by filter circuitry 206 c. The filter circuitry 206 c mayinclude a low-pass filter (LPF), although the scope of the embodimentsis not limited in this respect.

In some embodiments, the mixer circuitry 206 a of the receive signalpath and the mixer circuitry 206 a of the transmit signal path mayinclude two or more mixers and may be arranged for quadraturedown-conversion and/or upconversion respectively. In some embodiments,the mixer circuitry 206 a of the receive signal path and the mixercircuitry 206 a of the transmit signal path may include two or moremixers and may be arranged for image rejection (e.g., Hartley imagerejection). In some embodiments, the mixer circuitry 206 a of thereceive signal path and the mixer circuitry 206 a may be arranged fordirect downconversion and/or direct up-conversion, respectively. In someembodiments, the mixer circuitry 206 a of the receive signal path andthe mixer circuitry 206 a of the transmit signal path may be configuredfor super-heterodyne operation.

In some embodiments, the output baseband signals and the input basebandsignals may be analog baseband signals, although the scope of theembodiments is not limited in this respect. In some alternateembodiments, the output baseband signals and the input baseband signalsmay be digital baseband signals. In these alternate embodiments, the RFcircuitry 206 may include analog-to-digital converter (ADC) anddigital-to-analog converter (DAC) circuitry and the baseband circuitry204 may include a digital baseband interface to communicate with the RFcircuitry 206.

In some dual-mode embodiments, a separate radio IC circuitry may beprovided for processing signals for each spectrum, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 206 d may be afractional-N synthesizer or a fractional N/N+1 synthesizer, although thescope of the embodiments is not limited in this respect as other typesof frequency synthesizers may be suitable. For example, synthesizercircuitry 206 d may be a delta-sigma synthesizer, a frequencymultiplier, or a synthesizer comprising a phase-locked loop with afrequency divider.

The synthesizer circuitry 206 d may be configured to synthesize anoutput frequency for use by the mixer circuitry 206 a of the RFcircuitry 206 based on a frequency input and a divider control input. Insome embodiments, the synthesizer circuitry 206 d may be a fractionalN/N+1 synthesizer.

In some embodiments, frequency input may be provided by a voltagecontrolled oscillator (VCO), although that is not a requirement. Dividercontrol input may be provided by either the baseband circuitry 204 orthe applications processor 202 depending on the desired outputfrequency. In some embodiments, a divider control input (e.g., N) may bedetermined from a look-up table based on a channel indicated by theapplications processor 202.

Synthesizer circuitry 206 d of the RF circuitry 206 may include adivider, a delay-locked loop (DLL), a multiplexer and a phaseaccumulator. In some embodiments, the divider may be a dual modulusdivider (DMD) and the phase accumulator may be a digital phaseaccumulator (DPA). In some embodiments, the DMD may be configured todivide the input signal by either N or N+1 (e.g., based on a carry out)to provide a fractional division ratio. In some example embodiments, theDLL may include a set of cascaded, tunable, delay elements, a phasedetector, a charge pump and a D-type flip-flop. In these embodiments,the delay elements may be configured to break a VCO period up into Ndequal packets of phase, where Nd is the number of delay elements in thedelay line. In this way, the DLL provides negative feedback to helpensure that the total delay through the delay line is one VCO cycle.

In some embodiments, synthesizer circuitry 206 d may be configured togenerate a carrier frequency as the output frequency, while in otherembodiments, the output frequency may be a multiple of the carrierfrequency (e.g., twice the carrier frequency, four times the carrierfrequency) and used in conjunction with quadrature generator and dividercircuitry to generate multiple signals at the carrier frequency withmultiple different phases with respect to each other. In someembodiments, the output frequency may be a LO frequency (fLo). In someembodiments, the RF circuitry 206 may include an IQ/polar converter.

FEM circuitry 208 may include a receive signal path which may includecircuitry configured to operate on RF signals received from one or moreantennas 210, amplify the received signals and provide the amplifiedversions of the received signals to the RF circuitry 206 for furtherprocessing. FEM circuitry 208 may also include a transmit signal pathwhich may include circuitry configured to amplify signals fortransmission provided by the RF circuitry 206 for transmission by one ormore of the one or more antennas 210.

In some embodiments, the FEM circuitry 208 may include a TX/RX switch toswitch between transmit mode and receive mode operation. The FEMcircuitry may include a receive signal path and a transmit signal path.The receive signal path of the FEM circuitry may include a low-noiseamplifier (LNA) to amplify received RF signals and provide the amplifiedreceived RF signals as an output (e.g., to the RF circuitry 206). Thetransmit signal path of the FEM circuitry 208 may include a poweramplifier (PA) to amplify input RF signals (e.g., provided by RFcircuitry 206), and one or more filters to generate RF signals forsubsequent transmission (e.g., by one or more of the one or moreantennas 210.

In some embodiments, the communication device 200 may include additionalelements such as, for example, memory/storage, display, camera, sensor,and/or input/output (I/O) interface as described in more detail below.In some embodiments, the communication device 200 described herein maybe part of a portable wireless communication device, such as a personaldigital assistant (PDA), a laptop or portable computer with wirelesscommunication capability, a web tablet, a wireless telephone, asmartphone, a wireless headset, a pager, an instant messaging device, adigital camera, an access point, a television, a medical device (e.g., aheart rate monitor, a blood pressure monitor, etc.), or other devicethat may receive and/or transmit information wirelessly. In someembodiments, the communication device 200 may include one or more userinterfaces designed to enable user interaction with the system and/orperipheral component interfaces designed to enable peripheral componentinteraction with the system. For example, the communication device 200may include one or more of a keyboard, a keypad, a touchpad, a display,a sensor, a non-volatile memory port, a universal serial bus (USB) port,an audio jack, a power supply interface, one or more antennas, agraphics processor, an application processor, a speaker, a microphone,and other I/O components. The display may be an LCD or LED screenincluding a touch screen. The sensor may include a gyro sensor, anaccelerometer, a proximity sensor, an ambient light sensor, and apositioning unit. The positioning unit may communicate with componentsof a positioning network, e.g., a global positioning system (GPS)satellite.

The antennas 210 may comprise one or more directional or omnidirectionalantennas, including, for example, dipole antennas, monopole antennas,patch antennas, loop antennas, microstrip antennas or other types ofantennas suitable for transmission of RF signals. In some multiple-inputmultiple-output (MIMO) embodiments, the antennas 210 may be effectivelyseparated to take advantage of spatial diversity and the differentchannel characteristics that may result.

Although the communication device 200 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,field-programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs), radio-frequency integrated circuits (RFICs) andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements.

Embodiments may be implemented in one or a combination of hardware,firmware and software. Embodiments may also be implemented asinstructions stored on a computer-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. Some embodiments mayinclude one or more processors and may be configured with instructionsstored on a computer-readable storage device.

FIG. 3 is a block diagram of a communication device in accordance withsome embodiments. The device may be a UE, for example, such as the UEshown in FIG. 1. The physical layer circuitry 302 may perform variousencoding and decoding functions that may include formation of basebandsignals for transmission and decoding of received signals. Thecommunication device 300 may also include medium access control layer(MAC) circuitry 304 for controlling access to the wireless medium. Thecommunication device 300 may also include processing circuitry 306, suchas one or more single-core or multi-core processors, and memory 308arranged to perform the operations described herein. The physical layercircuitry 302, MAC circuitry 304 and processing circuitry 306 may handlevarious radio control functions that enable communication with one ormore radio networks compatible with one or more radio technologies. Theradio control functions may include signal modulation, encoding,decoding, radio frequency shifting, etc. For example, similar to thedevice shown in FIG. 2, in some embodiments, communication may beenabled with one or more of a WMAN, a WLAN, and a WPAN. In someembodiments, the communication device 300 can be configured to operatein accordance with 3GPP standards or other protocols or standards,including WiMax, WiFi, WiGig, GSM, EDGE, GERAN, UMTS, UTRAN, or other3G, 3G, 4G, 5G, etc. technologies either already developed or to bedeveloped. The communication device 300 may include transceivercircuitry 312 to enable communication with other external deviceswirelessly and interfaces 314 to enable wired communication with otherexternal devices. As another example, the transceiver circuitry 312 mayperform various transmission and reception functions such as conversionof signals between a baseband range and a Radio Frequency (RF) range.

The antennas 301 may comprise one or more directional or omnidirectionalantennas, including, for example, dipole antennas, monopole antennas,patch antennas, loop antennas, microstrip antennas or other types ofantennas suitable for transmission of RF signals. In some MIMOembodiments, the antennas 301 may be effectively separated to takeadvantage of spatial diversity and the different channel characteristicsthat may result.

Although the communication device 300 is illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingDSPs, and/or other hardware elements. For example, some elements maycomprise one or more microprocessors, DSPs, FPGAs, ASICs, RFICs andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements. Embodiments may be implemented in one or acombination of hardware, firmware and software. Embodiments may also beimplemented as instructions stored on a computer-readable storagedevice, which may be read and executed by at least one processor toperform the operations described herein.

FIG. 4 illustrates another block diagram of a communication device inaccordance with some embodiments. In alternative embodiments, thecommunication device 400 may operate as a standalone device or may beconnected (e.g., networked) to other communication devices. In anetworked deployment, the communication device 400 may operate in thecapacity of a server communication device, a client communicationdevice, or both in server-client network environments. In an example,the communication device 400 may act as a peer communication device inpeer-to-peer (P2P) (or other distributed) network environment. Thecommunication device 400 may be a UE, eNB, PC, a tablet PC, a STB, aPDA, a mobile telephone, a smart phone, a web appliance, a networkrouter, switch or bridge, or any communication device capable ofexecuting instructions (sequential or otherwise) that specify actions tobe taken by that communication device. Further, while only a singlecommunication device is illustrated, the term “communication device”shall also be taken to include any collection of communication devicesthat individually or jointly execute a set (or multiple sets) ofinstructions to perform any one or more of the methodologies discussedherein, such as cloud computing, software as a service (SaaS), othercomputer cluster configurations.

Examples, as described herein, may include, or may operate on, logic ora number of components, modules, or mechanisms. Modules are tangibleentities (e.g., hardware) capable of performing specified operations andmay be configured or arranged in a certain manner. In an example,circuits may be arranged (e.g., internally or with respect to externalentities such as other circuits) in a specified manner as a module. Inan example, the whole or part of one or more computer systems (e.g., astandalone, client or server computer system) or one or more hardwareprocessors may be configured by firmware or software (e.g.,instructions, an application portion, or an application) as a modulethat operates to perform specified operations. In an example, thesoftware may reside on a communication device readable medium. In anexample, the software, when executed by the underlying hardware of themodule, causes the hardware to perform the specified operations.

Accordingly, the term “module” is understood to encompass a tangibleentity, be that an entity that is physically constructed, specificallyconfigured (e.g., hardwired), or temporarily (e.g., transitorily)configured (e.g., programmed) to operate in a specified manner or toperform part or all of any operation described herein. Consideringexamples in which modules are temporarily configured, each of themodules need not be instantiated at any one moment in time. For example,where the modules comprise a general-purpose hardware processorconfigured using software, the general-purpose hardware processor may beconfigured as respective different modules at different times. Softwaremay accordingly configure a hardware processor, for example, toconstitute a particular module at one instance of time and to constitutea different module at a different instance of time.

Communication device (e.g., computer system) 400 may include a hardwareprocessor 402 (e.g., a central processing unit (CPU), a graphicsprocessing unit (GPU), a hardware processor core, or any combinationthereof), a main memory 404 and a static memory 406, some or all ofwhich may communicate with each other via an interlink (e.g., bus) 408.The communication device 400 may further include a display unit 410, analphanumeric input device 412 (e.g., a keyboard), and a user interface(UI) navigation device 414 (e.g., a mouse). In an example, the displayunit 410, input device 412 and UI navigation device 414 may be a touchscreen display. The communication device 400 may additionally include astorage device (e.g., drive unit) 416, a signal generation device 418(e.g., a speaker), a network interface device 420, and one or moresensors 421, such as a global positioning system (GPS) sensor, compass,accelerometer, or other sensor. The communication device 400 may includean output controller 428, such as a serial (e.g., universal serial bus(USB), parallel, or other wired or wireless (e.g., infrared (IR), nearfield communication (NFC), etc.) connection to communicate or controlone or more peripheral devices (e.g., a printer, card reader, etc.).

The storage device 416 may include a communication device readablemedium 422 on which is stored one or more sets of data structures orinstructions 424 (e.g., software) embodying or utilized by any one ormore of the techniques or functions described herein. The instructions424 may also reside, completely or at least partially, within the mainmemory 404, within static memory 406, or within the hardware processor402 during execution thereof by the communication device 400. In anexample, one or any combination of the hardware processor 402, the mainmemory 404, the static memory 406, or the storage device 416 mayconstitute communication device readable media.

While the communication device readable medium 422 is illustrated as asingle medium, the term “communication device readable medium” mayinclude a single medium or multiple media (e.g., a centralized ordistributed database, and/or associated caches and servers) configuredto store the one or more instructions 424.

The term “communication device readable medium” may include any mediumthat is capable of storing, encoding, or carrying instructions forexecution by the communication device 400 and that cause thecommunication device 400 to perform any one or more of the techniques ofthe present disclosure, or that is capable of storing, encoding orcarrying data structures used by or associated with such instructions.Non-limiting communication device readable medium examples may includesolid-state memories, and optical and magnetic media. Specific examplesof communication device readable media may include: non-volatile memory,such as semiconductor memory devices (e.g., Electrically ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM)) and flash memory devices; magnetic disks, such asinternal hard disks and removable disks; magneto-optical disks; RandomAccess Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples,communication device readable media may include non-transitorycommunication device readable media. In some examples, communicationdevice readable media may include communication device readable mediathat is not a transitory propagating signal.

The instructions 424 may further be transmitted or received over acommunications network 426 using a transmission medium via the networkinterface device 420 utilizing any one of a number of transfer protocols(e.g., frame relay, internet protocol (IP), transmission controlprotocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks may include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks (e.g., cellularnetworks), Plain Old Telephone (POTS) networks, and wireless datanetworks (e.g., IEEE 802.11 family of standards known as WiFi®, IEEE802.16 family of standards known as WiMax®), IEEE 802.15.4 family ofstandards, a LTE family of standards, a UMTS family of standards,peer-to-peer (P2P) networks, among others. In an example, the networkinterface device 420 may include one or more physical jacks (e.g.,Ethernet, coaxial, or phone jacks) or one or more antennas to connect tothe communications network 426. In an example, the network interfacedevice 420 may include a plurality of antennas to wirelessly communicateusing at least one of single-input multiple-output (SIMO), MIMO, ormultiple-input single-output (MISO) techniques. In some examples, thenetwork interface device 420 may wirelessly communicate using MultipleUser MIMO techniques. The term “transmission medium” shall be taken toinclude any intangible medium that is capable of storing, encoding orcarrying instructions for execution by the communication device 400, andincludes digital or analog communications signals or other intangiblemedium to facilitate communication of such software.

As above, a number of next generation challenges for PANs, whethercoordinated or not, exist. Such challenges may include avoidingintra-PAN collisions between downlink (DL) and uplink (UL) transmissionswithin a PAN that induce inter-tUE interference. A DL transmission maybe a transmission from the nUE to the tUE and a UL transmission may be atransmission from the tUE to the nUE. Other challenges include, reducinginter-PAN collisions or collision among PANs, fast power control andlink adaption multi-user multiplexing within each PAN, and timelyacknowledgment/non-acknowledgment feedback.

Table 1 provides one example of waveform and numerology of OFDMcommunications in the network shown in FIG. 1. The various options mayprovide a balance between FFT size and sampling rate.

TABLE 1 Numerology comparison Numerology Option 1 Option 2 Option 3Subcarrier 15 KHz 60 KHz 75 KHz spacing Sampling 30.72 MHz (20 30.72 MHz(20 38.4 MHz (20 rate (1/Ts) MHz, 2048-FFT) MHz, 512-FFT) MHz, 512-FFT)1.92 MHz (1.4 7.68 MHz (5 9.6 MHz (6 MHz, 128-FFT) MHz, 128-FFT) MHz,128-FFT) 4.8 MHz (2 MHz, 64-FFT) Number of 1200 300 240 used 72 72 72subcarriers 24 CP length 32 Ts = 32 Ts = 36Ts = 1.0417 us 1.0417 us0.9375 us Symbol (2048 + 32) Ts = (512 + 32)Ts = (512 + 36)Ts = length67.708 μs 7.708 μs 14.27 μs Number of 14 14 14 symbols per 28 35subframe 56 70 Subframe 1 ms 0.25 ms 0.2 ms length 0.5 ms 0.5 ms 1 ms 1ms Frame length 10 ms 2.5 ms 2 ms 5 ms 5 ms 10 ms 10 ms

FIG. 5 illustrates a frame structure in accordance with someembodiments. The frame structure may be used by any of the UEs shown inFIGS. 1-4. As shown, each 10 ms frame comprises ten 1 ms subframes,although other numerologies such as subframe lengths of 0.25 ms, 0.5 ms,or 2 ms can also be supported. Each subframe may be divided intomultiple physical resource blocks (PRB) in the frequency domain in whicheach PRB may occupy 3 subcarriers over one subframe. For a subcarrierspacing of 60 kHz and subframe duration of 1 ms, each PRB may occupy 180kHz over 1 ms. The PRBs may be grouped into subchannels in which eachsubchannel occupies 6 PRBs consecutive in the frequency domain. Theminimum system bandwidth is of the size of a subchannel.

The first subframe may be set to be a DL subframe, while the remainingsubframes may be either UL or DL subframes. The subframes may be dividedinto a number of sections. The first symbol in the subframe may be acommon control channel and may indicate whether the data channel is anUL or DL data channel Thus, the common control channel may be a DLcommon control channel independent of whether the data channel in thesubframe is UL or DL. The DL common control channel may be followed by aRequest to Send (RTS) (also called a Transmitter resource Acquisitionand Sounding (TAS)) channel and subsequently a Clear to Send (CTS) (alsocalled a Receiver resource Acknowledgement and Sounding (RAS)) channel.The RTS and CTS channel may be used for contention-based communicationsamong UEs of the PAN. The contention channels may be followed by an ULor DL data channel in which data is provided from one UE to the otherUE. This data may include ID and security information or user data. Thedata channel may be followed by an ACK/NACK in response to transmissionof the data. The channels may be transmitted on a Physical ResourceAllocation (PRA).

The various sections above may be separated by guard periods that reduceinter-symbol interference or permit the UE to switch between thetransmitter and receiver chains. At least some of the guard periods mayhave different lengths. For example, the guard periods between the DLcommon control channel and the RTS, between the RTS and the CTS andafter the ACK/NACK may occupy 1 symbol (17.7 μs total), the guard periodbetween the CTS and the data channel may occupy 1 symbol+(26.03 μstotal) and the guard period between the data channel and the ACK/NACKmay occupy 2 symbols.

A majority of the subchannels in the system may be used to provide databetween UEs. However, one or more of the subchannels may be reserved forcontrol signaling. For example, 1-2 resource elements (REs) of one ofthe central 6 PRBs in the first DL subframe of each frame may providebroadcast channel information, as well as paging and discoveryinformation. 1 RE may be defined as 1 subcarrier over 1 symbol, 1resource unit (RU) may be defined as 3 subcarriers over 4 consecutivesymbols (in total 12 REs). In some embodiments, the DL common controlchannel, the RTS, the CTS and the ACK may each occupy one RU, while thedata channel may occupy the 3 subcarriers over 34 symbols. The totalsubframe in this embodiment may thus extend over 56 symbols (includingthe above guard periods).

Design of reference signals for control and data signals in the subframemay be one challenge facing wearable systems. Time selectivity, inparticular, may present a challenge in implementing wirelesscommunication systems. To coherently detect the signals, receiversshould be aware of the channel variation. Thus, it may be desirable tocontinuously track and update the channel parameters. To estimate theunknown wireless channel parameters (channel quality for the allocatedresources) and detect user data coherently, reference signals may beinserted between the data signals in an approach called pilot-symbolassisted modulation (PSAM). The pilot symbols may be periodic messagesand may be in some embodiments Demodulation Reference Signals (DMRS).Unlike typical LTE networks, each nUE may transmit separate DMRSs forthe tUEs to detect. In some embodiments, the reference signals are powerboosted compared to user data signals (either that would be on the PRAor are on another PRA), exacerbating interference and other issues withother PANs. The complex representation of a wireless channel impulseresponse at the time domain is given by:

$\begin{matrix}{{h\left( {t,\tau} \right)} = {\sum\limits_{k = 0}^{L - 1}{{c_{k}(t)}{\delta\left( {\tau - \tau_{k}} \right)}}}} & (1)\end{matrix}$

where L is the number of wireless channel multipaths, τ_(k) is the delayof the kth path, and c_(k)(t) is the corresponding complex amplitude.Due to the motion of the UEs, c_(k)(t) can be modeled as wide-sensestationary and narrowband complex Gaussian process with average power ofσ_(k) ²'s, where its values are independently distributed. The frequencyresponse of the wireless channels at time t can be expressed as

$\begin{matrix}{{H\left( {t,f} \right)} = {\sum\limits_{k = 0}^{L - 1}{{c_{k}(t)}{e^{{- {j2}}\;\pi\; f\;\tau_{k}}.}}}} & (2)\end{matrix}$

To support a large number of nUE and tUE pairs on the sametime-frequency resources where inevitable contentions or collisionscause significant inter-PAN interference, efficient DMRS design isdesirable. Design principles of the DMRS include both randomization ofthe occurrences of inter-PAN DMRS collisions and robust DMRS locationsand patterns for the low-cost UEs. To this end, the DMRS locations foreach PAN may be randomly selected in the RU. This may occur even if alarge number of inter-PANs exist on the underlay network. This may alsoallow for robust channel estimation quality even if synchronization isless accurate in the lower-cost UEs. Although the discussion belowfocuses on the DMRS design for Option 2 with 512-FFT length as shown inTable 1, similar processes may be used for other options and other FFTlengths.

In addition to being used to estimate the channel quality (or channelcoefficients) and detect the user data coherently, DMRSs may also beused for link adaptation to select appropriate modulation coding schemes(MCSs). Increasing contention may occur as the number of nUE and tUEs(and thus PANs) increase, leading to an increase in the number ofcandidate DMRS locations and sequences. This may lead to selection ofDMRS patterns and locations to minimize the inter-PAN collisionoccurrences. DMRS, like other reference signals, may be transmitted onlyon assigned PRAs, with the assigned PRAs known via higher layersignaling or some other mechanism. FIG. 6 illustrates DMRS locations inaccordance with some embodiments. As shown in FIG. 6, two DMRSs aretransmitted on each RU, with the DMRS locations of 3×3 RUs beingillustrated. As above, the power of the DMRS signals in these locationsis boosted, compared to user data signals, to provide better channelestimate quality, so that each DMRS would be better to be placed ondistinctive OFDM symbols.

Each PAN may have a single nUE and one or more tUEs. Each nUE mayrandomly select the DMRS locations. The DMRS location may, in someembodiments, be selected using the temporary nUE ID to randomize thelocations, thereby reducing the collision probabilities. The temporarynUE ID may be generated using the MAC ID of the nUE, for example, byhashing the MAC ID. The locations/may be selected by:l=(nUE ID)mod N _(RS) ^(Set)

where N_(RS) ^(Set) is the number of available DMRS locations. In FIG.6, DMRS signals in which N_(RS) ^(Set)=16 (Option 2 with 20 MHzbandwidth), as an example. The temporary nUE ID may be determined by thecorresponding tUEs in the PAN during a discovery process in which thetUEs associate with the nUE. Alternatively, the DMRS location can alsobe chosen in a pseudo-random manner. In this case, the pseudorandomsequences c(i) may be defined by a length-31 Gold sequence. The outputsequence c(n) of length M_(PN), where n=0, 1, . . . , M_(pN)−1, may berepresented as:c(n)=(x ₁(n+N _(c))+x ₂(n+N _(c)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₁(n))mod 2

where N_(c)=bin2dec(nUEID) and x₁ (n) is initialized with x₁ (0)=1 andother values are zeros. The initial value of x₂ (n) is initialized withc_(init)=nUE ID, where nUE ID is the temporary nUE ID. The DMRSlocation, l, is selected byl=bin2dec(c([Q, . . . ,1])),

where Q=└log₂ N_(RS) ^(Set) ┘.

The reference signal sequence may be generated in a number of ways. Forexample, the reference signal sequence may be generated using apseudo-random sequence or a Zadoff-Chu sequence. The generated sequencesmay be mapped onto the modulation scheme with constant envelope. In someembodiments, for pseudo-random sequences with quadrature phase shiftkeying (QPSK), the reference signal sequence r_(l,d) (m) of the l^(th)DMRS location may be given by:

${{r_{l,d}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {\frac{j}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{2N_{Subframe}^{\max}} - 1}$

where the link indicator d is 0 for DL and 1 for UL and N_(Subframe)^(max) is the maximum number of DMRS within a subframe. The pseudorandom sequences c(i) may be defined in some embodiments by a length-31Gold sequence. The output sequence c(π) of length M_(PN), where n=0, 1,. . . , M_(PN)−1 may be given by:c(n)=(x ₁(n+N _(c))+x ₂(n+N _(c)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₁(n))mod 2

where N_(c)=1600 and x₁ (n) may be initialized with x₁ (0)=1 and othervalues are zeros. The initial values of x₂ (n) may be initialized withc_(init)=2^(K) ¹ ⁺⁶·(N_(RS) ^(Set)·(n_(s)+))+2^(K) ¹⁺¹·(N₂+1)·(n_(s)+1)+2·N₁+d, where n_(s) is the subframe number, the linkindicator d is 0 for DL and 1 for UL, N₁=bin2dec([K₁, . . . , 1]),N₂=bin2dec([K₂, . . . , 1]), and K₁ and K₂ are the number of the lastbits taken from the tUE ID and nUE ID, respectively. In otherembodiments, other bits of the IDs, such as the first bits may be used.The bits use may be the same between the tUE ID and the nUE ID (e.g.,the last two bits) in some embodiments. In other embodiments, bits maybe present in different positions (e.g., the last bits of the tUE ID andthe first bits of the nUE ID).

In some embodiments, a Zadoff-Chu (ZC) sequence may be used rather thana pseudorandom sequence. In this case, the ZC reference signal sequencer_(u,v) ^((α)) (n) may be defined by a cyclic shift a of a base sequencer _(u,v)(n) according to:

${{r_{u,v}^{(\alpha)}(n)} = {e^{- \frac{j\;\alpha\; 2\pi}{N_{RS}^{Set}}}{{\overset{\_}{r}}_{u,v}(n)}}},{0 \leq n \leq N_{RS}^{subframe}}$

where α∈{0, N_(RS) ^(Set)−1} and N_(RS) ^(Subframe) is the length ofavailable reference signals within a subframe. Multiple reference signalsequences may be defined from a single base sequence through differentvalues of α.r _(u,v) =x _(q)(n mod N _(RS) ^(subframe)),0≤n<N _(ZC)

where the link indicator v is 0 for DL and 1 for UL,x _(q)(m)=e ^(−jqm(m+1)/N) ^(ZC) ,0≤m<N _(ZC)−1q=u′+v·(−1)^(u′)u′=[bin2dec(M+1)] mod N _(ZC)M=concat(K ₂ bits of nUE ID; last L bits of wUE ID)

In some embodiments, M-ary phase shift keying (MPSK) may be used ratherthan QPSK. In this case, the pseudorandom sequences may differ fromthose for QPSK. Reference signal sequence r_(l,d) (m) of the l^(th) DMRSlocation may be given by:r _(1,d)(m)=e ^(−j·φ(m)/2π) ,m=0,1, . . . ,N _(Subframe) ^(max)−1

where the link indicator d is 0 for DL and 1 for UL and N_(Subframe)^(max) is the maximum number of DMRS within a subframe. The mappingfunction φ(m) may be defined as:

${{\varphi(m)} = {k \cdot \frac{2\pi}{M}}},$

where k is equal to bin2dec(c([P, . . . , 1]+m·P)), where P=log₂ M. Notethat M is the power of 2. The pseudo random sequences c(i), as above,may be defined by a length-31 Gold sequence. The output sequence c(n) oflength M_(PN), where n=0, 1, . . . , M_(PN)−1 may be given by:c(n)=(x ₁(n+N _(c))+x ₂(n+N _(c)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₁(n))mod 2

where N_(c)=1600 and x₁ (n) is initialized with x₁ (0)=1 and othervalues are zeros. The initial values of x₂ (n) is initialized withc_(init)=2^(K) ¹ ⁺⁶·(N_(RS) ^(Set)·(n_(s)+1))+2^(K) ¹⁺¹·(N₂+1)·(n_(s)+1)+2·N₁+d, where n_(s) is the subframe number,N₁=bin2dec([K₁, . . . , 1]), N₂=bin2dec([K₂, . . . , 1]), and K₁ and K₂may be the number of the last bits taken from the tUE ID and nUE ID,respectively. In other embodiments, as above, the bits may be different.

Thus, after the nUE selects the DMRS location and sequence, the tUEswithin the PAN may use the same location and different sequences. Thesequences may differ as the seed of random sequence may be different.The sequence can be different in depending on each tUE ID. The nUE andtUE may have the same transmission functionality and detect the DMRSs,but location selection may be performed only by the nUE.

Simulation results of the DMRS performance show the criteria to todecide locations of the DMRSs out of the total number of candidates,which cardinality consists of

$\quad\begin{pmatrix}12 \\k\end{pmatrix}$combinations, where k is the number of DMRSs in each RU. Since k is setto 2, the number of unique DMRS locations is 66. Table 2, below providesthe simulation parameters used.

TABLE 2 Simulation parameters for link-level simulation SimulationSimulation Parameters Values Parameters Values Carrier (MHz) 2000 Framestructure Option 2 Symbol duration (us) 17.7 FFT size 512    Bandwidth(MHz) 20 Channel model EPA, TU, Exp 3 km/h Antenna configuration 1 Txand 1 Rx Doppler (Hz) 5.56 FEC Data channel: 1/3 Modulation Datachannel: Convolutional codes BPSK, QPSK, as mother code 16QAM, 64QAM([1.33, 171, (165)]) Channel estimation 2-D Wiener filters Resource 1,2, and 3 PRBs (B-by-B) allocations Average, LS estimate (1 PRA)

The simulations were performed to indicate the error performance fordata channels without a timing mismatch (having a timing advance ofzero) under frequency-selective channels. FIG. 7 illustrates DMRSlocations in a RU in accordance with some embodiments. To determineoptimized DMRS locations on an RU, the channel estimators may besimulated for various DMRS locations with two reference signals on anRU. As above, a single RU is 3 subcarriers in width and 4 symbols inlength. The examples shown in FIG. 7 are not exclusive—they merelyreflect individual layouts of the 66 possible DMRS locations. Forexample, DMRS location #11 in FIG. 7 illustrates the DMRS layout shownin the upper left embodiment shown in FIG. 6. For Extended Pedestrian Amodel (EPA)-3 km/h, channel estimators using an average method showsimilar performance of minimum mean square error (MMSE) channelestimators since the wireless channel characteristics of EPA at thefrequency domain is less frequency selective. However, worse MSE isobserved in the average method, as channel estimators with average donot match with channel statistics, especially in a high signal-to-noiseratio (SNR) region.

The simulations were performed to indicate the error performance fordata channels with a timing mismatch under frequency-selective channels.The synchronization of wearable or IoT UEs (tUEs) may not be accurateenough compared to normal cellular or high-end devices because the tUEsmay be designed to be cost-effective and power-effective. Thus, thesymbol timing mismatch should be considered for DMRS designs as timingmismatch may occur more frequently. The simulations indicate that errorperformance may vary depending on the DMRS locations when symbol timingmismatch exists. In such embodiments, error performance may be improvedif the DMRSs are placed on different subcarriers and different OFDMsymbols in an RU when wireless channels are more frequency-selective.

The effect of timing mismatch on error performance for an exponentialchannel, rather using EPA channels, was also measured to make thechannel marginally selective,

${{p_{d}(\tau)} = e^{- \frac{\tau}{2}}},{\tau = {\left\{ {0,2,\ldots\;,24} \right\} \cdot {T_{s}.}}}$

In case of 16 sample timing mismatches, MMSE methods showed about 2.5 dBdegradation from the error performance with perfect channel information,while the average method showed a slightly worse performance than thatof the MMSE method. Least squares (LS) methods showed 3 dB degradationfrom the error performance with MMSE methods. However, the channelestimator with MMSE methods employs the channel statistics, which may bemeasured empirically in practical systems, while the estimator withaverage or LS methods does not use such information and thus may be morepractical.

FIG. 8 illustrates a flowchart of DMRS generation in accordance withsome embodiments. The method shown in FIG. 8 may be performed by any ofthe UEs described in FIGS. 1-4. Examples of possible DMRS locationsultimately selected may be shown in FIG. 6.

At operation 802, the nUE may communicate with a base station. The basestation may be an eNB or other LTE base station or a 5G base station.The base station may be a macro base station or a micro (pico/nano) basestation. The communications may include both data and controlcommunications.

At operation 804, the nUE may determine whether any tUE is associatedwith the nUE. If not, the nUE may determine that there is no reason totransmit its own DMRS (referred to as nDMRS) as no tUEs are around torespond to the nDRMS. The nUE may store tUEs that have associated withthe nUE via a discovery mechanism to determine whether tUEs are present.If a tUE has associated with the nUE but has not exchanged data orcontrol signals with the nUE in a predetermined amount of time (or hasspecifically sent a de-association signal to the nUE), the nUE maydetermine that the tUE is no longer associated with the nUE. In otherembodiments, the nUE may transmit nDMRS independent of whether tUEs arepresent.

At operation 806, after having determined that at least one tUE ispresent, the nUE may determine whether nDMRS have already beentransmitted to the tUE. Once determined, the nUE may continue to use thesame nDMRS. Alternatively, the nUE may change the nDMRS from time totime, based on an event such as a predetermined amount of time passing,a predetermined number of tUEs in the PAN or a predetermined density ofneighboring PANs/nUEs.

If previously determined nDMRS are not to be used, the nUE may atoperation 808 select nDMRS locations in a RU of a PRA in a shared datachannel. The nDMRS locations may be selected to minimize inter-PANcollision occurrences. In some embodiments, the nDMRS location selectionis randomized. In some embodiments, the temporary nUE ID, the MAC IDand/or a combination of IDs may be used to determine the randomization.In some embodiments, the ID or combination may be known to the tUEs topermit the tUEs to determine the nDMRS locations. In other embodiments,the nDMRS locations may be indicated to the tUEs via higher layersignaling. The nDMRS locations may, in some embodiments, be randomizedusing a pseudo-random function. For example, the nDMRS locations may bedefined by a length-31 Gold sequence. In some embodiments, the nDMRSfrom different nUEs are disposed on different subcarriers and differentOFDM symbols in an RU.

Once the nDMRS locations are determined, the nDMRS sequence may begenerated. nDMRS sequence generation may be independent of the manner inwhich the nDMRS locations are selected. In some embodiments, the nDMRSsequences may be pseudo-random. The random sequence may permit nDMRSsequences to be distinct between PANs and within the PAN. In someembodiments, according to the pseudo-random nDMRS sequences, themodulation with constant envelope (e.g., MPSK, QPSK) may be selected forcommunications between the nUE and the tUE pairs. Alternatively, thenDMRS sequences may be based on a Zadoff-Chu sequence. In someembodiments, the placement of the nDMRS may depend on placement of thenDMRS of neighboring nUEs.

After generation of the nDMRS, at operation 810, different operationsmay occur dependent on whether the nDMRS are UL or DL nDMRS. Some of thenDMRS characteristics may remain the same between UL and DL nDMRStransmissions, while others may differ.

If the nDMRS are DL nDMRS, at operation 812, the nDMRS may betransmitted by the nUE on the shared data channel. The power of thenDMRS may be higher than that of data communications between the nUE andthe tUE. The nDMRS locations and sequences can be transmittedperiodically, e.g., every n subframes or m RUs in a subframe, with theperiod configured by higher layer signaling or being a configurationparameter broadcast by the nUE or base station associated with the nUE.In some circumstances, however, the nDMRS may not be transmitted on thedata shared channel; for example if the nUE determines that theprobability for collision or contention is less than a predeterminedpercent. The probability determined by the nUE may be based on thenumber of tUEs in the PAN and/or the density of neighboring PANs. Insuch embodiments when DMRSs are applied only to the control channels(e.g., common control, TAS, RAS, and ACK channels), channel estimatesfor the shared data channel can be obtained by DMRS on the controlchannel and demodulated control signals, in particular the TAS (RTS)channel.

If the DMRS is removed from the data shared channel, the channelcoefficients from the TAS channel can be used for coherent detection onthe data shared channels. In other embodiments, if the collision orcontention probability is less than a predetermined value, use of thecontrol channels (common control, TAS, RAS, and ACK channels) fortransmission of the DMRS may be avoided. In some embodiments, the DMRScan be inserted on every k RU on the data shared channel instead ofsending DMRSs on every RU.

The tUEs associated with the nDMRS may decode the nDMRS. The tUE maymeasure the RSSI, SNR, SINR, BLER or other characteristic of the nDMRSto determine information of the channel quality. The tUE may thenprovide the information determined from the DMRS to the nUE at operation814.

If the nDMRS are UL nDMRS, at operation 816, the nUE may receive thenDMRS from the tUE. That is, the tUE may generate the nDMRS. In thiscase, as above, a similar nDMRS pattern (i.e., the same nDMRS locations)can be used by the tUE side for UL data transmission. However, while thenDMRS location may be selected by the nUE (or using information such asthe nUE temporary ID), the nDMRS sequence generated and transmitted bythe tUE may be different than that generated and transmitted by the nUE.In some embodiments, the seed used to generate the pseudo-randomsequence may be different (e.g., the nUE temporary ID vs. the tUEtemporary ID). In some embodiments, the UL and DL nDMRS locations may bedifferent but can be paired based on a predetermined mapping rule, suchas (DL, UL)→(R0, R1), (R1, R2), etc.

At operation 818, the nUE may determine the appropriate modulationscheme or MCS to use. The nUE may make the determination based on thechannel quality information determined by the nUE based on the UL nDMRSfrom the UE or from the channel quality information determined by thetUE from the DL nDMRS measurements made by the tUE.

EXAMPLES

Example 1 is an apparatus of user equipment (UE), the apparatuscomprising: memory; and processing circuitry in communication with thememory and arranged to: randomize Demodulation Reference Signal (DMRS)locations of a DMRS in a resource unit (RU) of a predetermined PhysicalResource Allocation (PRA) of a shared channel for transmission toanother UE; generate DMRS sequences for transmission to the other UE inthe DMRS locations; and in response to transmission of the DMRS, decodechannel quality information received from the other UE based on theDMRS.

In Example 2, the subject matter of Example 1 optionally includes,wherein: the DMRS sequences are random sequences defined by one of alength-31 Gold sequence or a Zadoff-Chu sequence.

In Example 3, the subject matter of Example 2 optionally includes,wherein: each random sequence is mapped onto M-ary phase shift keying(MPSK) signal modulation.

In Example 4, the subject matter of any one or more of Examples 1-3optionally include, wherein: each RU of the PRA comprises a pair of DMRShaving a transmission power higher than that of data signals in the RUof another PRA in the shared channel.

In Example 5, the subject matter of any one or more of Examples 1-4optionally include, wherein the processing circuitry is configured to:replicate the DMRS locations every predetermined number of subframes,and configure the predetermined number of subframes by higher layersignaling or broadcast as a configuration parameter.

In Example 6, the subject matter of any one or more of Examples 1-5optionally include, wherein the processing circuitry is configured to:replicate the DMRS locations every predetermined number of RUs of theshared channel in a subframe, the predetermined number being an integergreater than 1, and configure the predetermined number of RUs by higherlayer signaling or broadcast as a configuration parameter.

In Example 7, the subject matter of any one or more of Examples 1-6optionally include, wherein the shared channel is a shared data channeland the processing circuitry is configured to: condition transmission ofthe DMRS based on at least one of a collision or contention probability,the at least one of a collision or contention probability based on atleast one of a number of other UEs in a personal area network (PAN)associated with the UE or a density of neighboring PANs associated withother UEs, and in response to a determination that the at least one ofthe collision or contention probability is less than a predeterminedvalue, avoid use of the shared data channel for transmission of theDMRS.

In Example 8, the subject matter of any one or more of Examples 1-7optionally include, wherein: the other UE is a wearable UE, and theprocessing circuitry is configured to communicate data from the other UEto a base station.

In Example 9, the subject matter of any one or more of Examples 1-8optionally include, wherein: the DMRS locations are determined based ona temporary ID of the UE.

In Example 10, the subject matter of any one or more of Examples 1-9optionally include, wherein the processing circuitry is configured to:determine whether any other UE is associated with the UE to form apersonal area network (PAN), and in response to a determination that theUE is unassociated with the other UE, avoid transmission of the DMRS.

In Example 11, the subject matter of any one or more of Examples 1-10optionally include, wherein: the shared channel comprises at least oneof a common control channel, a Transmitter resource Acquisition andSounding (TAS) channel, a Receiver resource Acknowledgement and Sounding(RAS) channel, and an acknowledgment (ACK) channel.

In Example 12, the subject matter of any one or more of Examples 1-11optionally include, wherein: the DMRS locations are disposed on at leastone of different subcarriers or symbols in the RU.

In Example 13, the subject matter of any one or more of Examples 1-12optionally include, wherein: the processing circuitry comprises abaseband processor, and the apparatus further comprises a transceiverconfigured to communicate with the other UE.

Example 14 is an apparatus of user equipment (UE), the apparatuscomprising: memory; and processing circuitry in communication with thememory and arranged to: detect a Demodulation Reference Signal (DMRS)received from another UE, the DMRS being random sequences and disposedat locations in a resource unit (RU) of a predetermined PhysicalResource Allocation (PRA) in a shared data or control channel; measurethe DMRS; and encode channel quality information based on the measuredDMRS for transmission to the other UE.

In Example 15, the subject matter of Example 14 optionally includes,wherein: each RU of the PRA comprises a pair of DMRS having atransmission power higher than that of data signals in the RU of anotherPRA in the shared data or control channel.

In Example 16, the subject matter of any one or more of Examples 14-15optionally include, wherein: the DMRS locations are disposed on at leastone of different subcarriers or symbols in the RU.

In Example 17, the subject matter of any one or more of Examples 14-16optionally include, wherein: the DMRS locations are repeated everypredetermined number of subframes, and the processing circuitry isconfigured to detect the predetermined number of subframes from one of:higher layer signaling or as a configuration parameter in a broadcast.

In Example 18, the subject matter of any one or more of Examples 14-17optionally include, wherein: the DMRS locations are repeated everypredetermined number of RUs of the shared data channel in a subframe,the predetermined number being an integer greater than 1, and theprocessing circuitry is configured to detect the predetermined number ofRUs from one of: higher layer signaling or as a configuration parameterin a broadcast.

In Example 19, the subject matter of any one or more of Examples 14-18optionally include, wherein: the apparatus is a wearable UE and theprocessing circuitry is configured to communicate data through the otherUE to a base station.

In Example 20, the subject matter of any one or more of Examples 14-19optionally include, wherein: the DMRS locations are determined based ona temporary ID of the other UE.

Example 21 is a computer-readable storage medium that storesinstructions for execution by one or more processors of a user equipment(UE), the one or more processors to: randomize Demodulation ReferenceSignal (DMRS) locations of a DMRS in a resource unit of a predeterminedPhysical Resource Allocation (PRA) of a shared channel for transmissionto another UE; generate random DMRS sequences for transmission to theother UE in the DMRS locations; and in response to transmission of theDMRS, decode channel quality information from the other UE based on theDMRS.

In Example 22, the subject matter of Example 21 optionally includes,wherein: the DMRS locations are disposed on at least one of differentsubcarriers or symbols in the RU.

In Example 23, the subject matter of any one or more of Examples 21-22optionally include, wherein: the DMRS locations are determined based ona temporary ID of the UE.

In Example 24, the subject matter of any one or more of Examples 21-23optionally include, wherein the instructions further configure the oneor more processors to: replicate the DMRS locations every predeterminednumber of subframes, and one of: configure the predetermined number ofsubframes by higher layer signaling or broadcast as a configurationparameter.

In Example 25, the subject matter of any one or more of Examples 21-24optionally include, wherein the instructions further configure the oneor more processors to: replicate the DMRS locations every predeterminednumber of RUs of the shared data channel in a subframe, thepredetermined number being an integer greater than 1, and configure thepredetermined number of RUs by higher layer signaling or broadcast as aconfiguration parameter.

In Example 26, the subject matter of any one or more of Examples 21-25optionally include, wherein the instructions further configure the oneor more processors to: condition transmission of the DMRS based on atleast one of a collision or contention probability, the at least one ofa collision or contention probability based on at least one of a numberof other UEs in a personal area network (PAN) associated with the UE ora density of neighboring PANs associated with other UEs, and in responseto a determination that the at least one of the collision or contentionprobability is less than a predetermined value, avoid use of the sharedchannel for transmission of the DMRS.

In Example 27, the subject matter of any one or more of Examples 21-26optionally include, wherein: the shared channel comprises a shared datachannel.

In Example 28, the subject matter of any one or more of Examples 21-27optionally include, wherein: the shared channel comprises at least oneof a common control channel, a Transmitter resource Acquisition andSounding (TAS) channel, a Receiver resource Acknowledgement and Sounding(RAS) channel, and an acknowledgment (ACK) channel.

Example 29 is an apparatus of a user equipment (UE), the apparatuscomprising: means for randomizing Demodulation Reference Signal (DMRS)locations of a DMRS in a resource unit of a predetermined PhysicalResource Allocation (PRA) of a shared channel for transmission toanother UE; means for generating random DMRS sequences for transmissionto the other UE in the DMRS locations; and means for decoding, inresponse to transmission of the DMRS, channel quality information fromthe other UE based on the DMRS.

In Example 30, the subject matter of Example 29 optionally includes,wherein: the DMRS locations are disposed on at least one of differentsubcarriers or symbols in the RU.

In Example 31, the subject matter of any one or more of Examples 29-30optionally include, wherein: the DMRS locations are determined based ona temporary ID of the UE.

In Example 32, the subject matter of any one or more of Examples 29-31optionally include, further comprising: means for replicating the DMRSlocations every predetermined number of subframes, and means forconfiguring the predetermined number of subframes by higher layersignaling or broadcast as a configuration parameter.

In Example 33, the subject matter of any one or more of Examples 29-32optionally include, further comprising: means for replicating the DMRSlocations every predetermined number of RUs of the shared data channelin a subframe, the predetermined number being an integer greater than 1,and means for configuring the predetermined number of RUs by higherlayer signaling or broadcast as a configuration parameter.

In Example 34, the subject matter of any one or more of Examples 29-33optionally include, further comprising: means for conditioningtransmission of the DMRS based on at least one of a collision orcontention probability, the at least one of a collision or contentionprobability based on at least one of a number of other UEs in a personalarea network (PAN) associated with the UE or a density of neighboringPANs associated with other UEs, and in response to a determination thatthe at least one of the collision or contention probability is less thana predetermined value, means for avoiding use of the shared channel fortransmission of the DMRS.

In Example 35, the subject matter of any one or more of Examples 29-34optionally include, wherein: the shared channel comprises a shared datachannel.

In Example 36, the subject matter of any one or more of Examples 29-35optionally include, wherein: the shared channel comprises at least oneof a common control channel, a Transmitter resource Acquisition andSounding (TAS) channel, a Receiver resource Acknowledgement and Sounding(RAS) channel, and an acknowledgment (ACK) channel.

Example 37 is an method of providing a Demodulation Reference Signal(DMRS) from a user equipment (UE), the method comprising: randomizingDMRS locations of a DMRS in a resource unit of a predetermined PhysicalResource Allocation (PRA) of a shared channel for transmission toanother UE; generating random DMRS sequences for transmission to theother UE in the DMRS locations; and decoding, in response totransmission of the DMRS, channel quality information from the other UEbased on the DMRS.

In Example 38, the subject matter of Example 37 optionally includes,wherein: the DMRS locations are disposed on at least one of differentsubcarriers or symbols in the RU.

In Example 39, the subject matter of any one or more of Examples 37-38optionally include, wherein: the DMRS locations are determined based ona temporary ID of the UE.

In Example 40, the subject matter of any one or more of Examples 37-39optionally include, further comprising: replicating the DMRS locationsevery predetermined number of subframes, and configuring thepredetermined number of subframes by higher layer signaling or broadcastas a configuration parameter.

In Example 41, the subject matter of any one or more of Examples 37-40optionally include, further comprising: replicating the DMRS locationsevery predetermined number of RUs of the shared data channel in asubframe, the predetermined number being an integer greater than 1, andconfiguring the predetermined number of RUs by higher layer signaling orbroadcast as a configuration parameter.

In Example 42, the subject matter of any one or more of Examples 37-41optionally include, further comprising: conditioning transmission of theDMRS based on at least one of a collision or contention probability, theat least one of a collision or contention probability based on at leastone of a number of other UEs in a personal area network (PAN) associatedwith the UE or a density of neighboring PANs associated with other UEs,and in response to a determination that the at least one of thecollision or contention probability is less than a predetermined value,avoiding use of the shared channel for transmission of the DMRS.

In Example 43, the subject matter of any one or more of Examples 37-42optionally include, wherein: the shared channel comprises a shared datachannel.

In Example 44, the subject matter of any one or more of Examples 37-43optionally include, wherein: the shared channel comprises at least oneof a common control channel, a Transmitter resource Acquisition andSounding (TAS) channel, a Receiver resource Acknowledgement and Sounding(RAS) channel, and an acknowledgment (ACK) channel.

Although an embodiment has been described with reference to specificexample embodiments, it will be evident that various modifications andchanges may be made to these embodiments without departing from thebroader scope of the present disclosure. Accordingly, the specificationand drawings are to be regarded in an illustrative rather than arestrictive sense. The accompanying drawings that form a part hereofshow, by way of illustration, and not of limitation, specificembodiments in which the subject matter may be practiced. Theembodiments illustrated are described in sufficient detail to enablethose skilled in the art to practice the teachings disclosed herein.Other embodiments may be utilized and derived therefrom, such thatstructural and logical substitutions and changes may be made withoutdeparting from the scope of this disclosure. This Detailed Description,therefore, is not to be taken in a limiting sense, and the scope ofvarious embodiments is defined only by the appended claims, along withthe full range of equivalents to which such claims are entitled.

The subject matter may be referred to herein, individually and/orcollectively, by the term “embodiment” merely for convenience andwithout intending to voluntarily limit the scope of this application toany single inventive concept if more than one is in fact disclosed.Thus, although specific embodiments have been illustrated and describedherein, it should be appreciated that any arrangement calculated toachieve the same purpose may be substituted for the specific embodimentsshown. This disclosure is intended to cover any and all adaptations orvariations of various embodiments. Combinations of the aboveembodiments, and other embodiments not specifically described herein,will be apparent to those of skill in the art upon reviewing the abovedescription.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, UE,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separate embodiment.

What is claimed is:
 1. A user equipment device (UE), comprising: memory;and processing circuitry in communication with the memory and configuredto cause the UE to: randomize Demodulation Reference Signal (DMRS)locations of a DMRS in a resource unit (RU) of a Physical ResourceAllocation (PRA) of a shared channel for transmission to an other UE,wherein the DMRS locations are determined based on a temporary ID of theUE; generate DMRS sequences for transmission to the other UE in the DMRSlocations; and in response to transmission of the DMRS, decodeinformation received from the other UE based on characteristics ofreceived DMRS transmissions.
 2. The UE of claim 1, wherein the DMRSsequences are random sequences defined by one of a length-31 Goldsequence or a Zadoff-Chu sequence.
 3. The UE of claim 2, wherein eachrandom sequence is mapped onto M-ary phase shift keying (MPSK) signalmodulation.
 4. The UE of claim 2, wherein respective RUs of the PRAcomprise respective pairs of DMRS having a transmission power higherthan that of data signals in a first RU of another PRA in the sharedchannel.
 5. The UE of claim 2, wherein the processing circuitry isfurther configured to cause the UE to: replicate the DMRS locationsevery predetermined number of subframes; and configure the predeterminednumber of subframes by higher layer signaling or by broadcast as aconfiguration parameter.
 6. The UE of claim 2, wherein the processingcircuitry is further configured to cause the UE to: replicate the DMRSlocations every predetermined number of RUs of the shared channel in asubframe; and configure the predetermined number of RUs by higher layersignaling or by broadcast as a configuration parameter.
 7. The UE ofclaim 6, wherein the predetermined number is an integer greater than 1.8. The UE of claim 2, wherein the shared channel is a shared datachannel and the processing circuitry is further configured to cause theUE to: condition transmission of the DMRS based on at least one of acollision or contention probability, wherein the at least one of thecollision or contention probability is based on at least one of a numberof other UEs in a personal area network (PAN) associated with the UE ora density of neighboring PANs associated with other UEs; and in responseto a determination that the at least one of the collision or contentionprobability is less than a predetermined value, avoid use of the shareddata channel for transmission of the DMRS.
 9. The UE of claim 2, whereinthe other UE is a wearable UE, and wherein the processing circuitry isfurther configured to cause the UE to communicate data from the other UEto a base station.
 10. The UE of claim 2, wherein the processingcircuitry is further configured to cause the UE to: determine whetherany other UE is associated with the UE to form a personal area network(PAN); and in response to a determination that the UE is unassociatedwith the other UE, avoid transmission of the DMRS.
 11. The UE of claim2, wherein the shared channel comprises at least one of a common controlchannel, a Transmitter resource Acquisition and Sounding (TAS) channel,a Receiver resource Acknowledgement and Sounding (RAS) channel, or anacknowledgment (ACK) channel.
 12. The UE of claim 2, wherein the DMRSlocations are disposed on at least one of different subcarriers orsymbols in the RU.
 13. The UE of claim 2, wherein the processingcircuitry comprises a baseband processor; and wherein the UE furthercomprises a transceiver configured to communicate with the other UE. 14.An apparatus, comprising: memory; and a processor in communication withthe memory and configured to cause a user equipment device (UE) to:detect a Demodulation Reference Signal (DMRS) received from an other UE,wherein the DMRS are random sequences and disposed at locations in aresource unit (RU) of a Physical Resource Allocation (PRA) of a sharedchannel, wherein the locations are determined based on a temporary ID ofthe other UE; measure the DMRS; and encode channel quality informationbased on the measured DMRS for transmission to the other UE.
 15. Theapparatus of claim 14, wherein respective RUs of the PRA compriserespective pairs of DMRS having a transmission power higher than that ofdata signals in a first RU of another PRA in the shared channel.
 16. Theapparatus of claim 14, wherein the locations are disposed on at leastone of different subcarriers or symbols in the RU.
 17. The apparatus ofclaim 14, wherein the locations are repeated at a predetermined numberof subframes; and wherein the processor is further configured to causethe UE to detect the predetermined number of subframes from one ofhigher layer signaling or as a configuration parameter in a broadcast.18. The apparatus of claim 14, wherein the locations are repeated at apredetermined number of RUs of the shared channel in a subframe; andwherein the processor is further configured to cause the UE to detectthe predetermined number of RUs is from one of: higher layer signalingor as a configuration parameter in a broadcast.
 19. The apparatus ofclaim 18, wherein the predetermined number is an integer greater than 1.20. The apparatus of claim 14, wherein the apparatus is a wearable UE;and wherein the processor is further configured to cause the UE tocommunicate data through the other UE to a base station.
 21. Anon-transitory computer-readable storage medium that stores instructionsfor execution by one or more processors of a user equipment (UE), theone or more processors to: randomize-Demodulation Reference Signal(DMRS) locations of a DMRS in a resource unit (RU) of a PhysicalResource Allocation (PRA) of a shared channel for transmission to another UE, wherein the DMRS locations are determined based on a temporaryID of the UE; generate DMRS sequences for transmission to the other UEin the DMRS locations; and in response to transmission of the DMRS,decode information received from the other UE based on characteristicsof received DMRS transmissions.
 22. The non-transitory computer-readablestorage medium of claim 21, wherein the DMRS locations are disposed onat least one of different subcarriers or symbols in the RU.
 23. Thenon-transitory computer-readable storage medium of claim 21, wherein theDMRS sequences are random sequences defined by one of a length-31 Goldsequence or a Zadoff-Chu sequence.
 24. The non-transitorycomputer-readable storage medium of claim 21, wherein the instructionsare further executable to configure the one or more processors to:replicate the DMRS locations every predetermined number of subframes,and configure the predetermined number of subframes by higher layersignaling or broadcast as a configuration parameter.
 25. Thenon-transitory computer-readable storage medium of claim 21, wherein theinstructions are further executable to configure the one or moreprocessors to: replicate the DMRS locations every predetermined numberof RUs of the shared channel in a subframe, wherein the predeterminednumber is an integer greater than 1, and configure the predeterminednumber of RUs by higher layer signaling or broadcast as a configurationparameter.
 26. The non-transitory computer-readable storage medium ofclaim 21, wherein the instructions are further executable to configurethe one or more processors to: condition transmission of the DMRS basedon at least one of a collision or contention probability, the at leastone of a collision or contention probability based on at least one of anumber of other UEs in a personal area network (PAN) associated with theUE or a density of neighboring PANs associated with other UEs; and inresponse to a determination that the at least one of the collision orcontention probability is less than a predetermined value, avoid use ofthe shared channel for transmission of the DMRS.